1. Field of the Invention
The present invention relates to a light source apparatus and a method for controlling the same.
2. Description of the Related Art
Color image display apparatuses have a color liquid crystal panel with a color filter and a light source apparatus (backlight apparatus) that projects white light onto the back surface of the color liquid crystal panel.
Conventionally, fluorescent lamps such as cold cathode fluorescent lamps (CCFLs) have been mainly used as the light sources of light source apparatuses. In recent years, however, light emitting diodes (LEDs) excellent in power consumption, service life, color reproducibility, and environmental load have become widespread as the light sources of the light source apparatuses.
In general, the light source apparatuses with the LEDs as their light sources (LED backlight apparatuses) have many LEDs. Japanese Patent Application Laid-open No. 2001-142409 discloses the LED backlight apparatus with a plurality of light emission units each having one or more LEDs. In addition, Japanese Patent Application Laid-open No. 2001-142409 discloses the control of brightness for each of the light emission units. With a reduction in the light emission brightness of the light emission units that project light to a region where a dark image is to be displayed in the screen of a color image display apparatus, power consumption is reduced and image contrast is enhanced. Such brightness control for each of the light emission units according to the characteristics of an image is called local dimming control.
The light source apparatuses suffer from a problem in which the light emission brightness of the light emission units is changed. The change in the light emission brightness is caused by, for example, a change in the light emission characteristics of the light sources due to a change in temperature, aging degradation in the light sources, or the like. In the light source apparatuses with the plurality of light emission units, the light emission brightness of the plurality of light emission units is fluctuated (caused to have brightness unevenness) with a fluctuation in the temperature or the aging degradation degree of the plurality of light emission units.
As a method for reducing the change in the light emission brightness and the brightness unevenness, there has been known a method for adjusting the light emission brightness of the light emission units using light sensors. Specifically, the method includes arranging the light sensors that detect light, which is reflected by the optical sheet (optical member) of the light source apparatuses and returned to the side of the light emission units, among light emitted from the light source apparatuses and adjusting the light emission brightness of the light emission units based on the detection values of the light sensors. In the light source apparatuses with the plurality of light emission units, the light emission units are turned on in a sequential order, and the reflected light is detected by the light sensors for each of the light emission units to adjust the light emission brightness. Such technology is disclosed in, for example, in Japanese Patent Application Laid-open No. 2011-27941.